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Piezoelectric MEMS Resonator Measurement and Characterization. April 6, 2004. Joung-Mo Kang, David Carter, Doug White, and Amy Duwel The Charles Stark Draper Laboratory. Presentation Overview. Background and device models Filter design L-Bar measurements Parasitic investigations

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piezoelectric mems resonator measurement and characterization
Piezoelectric MEMS Resonator Measurement and Characterization

April 6, 2004

Joung-Mo Kang, David Carter, Doug White, and Amy Duwel

The Charles Stark Draper Laboratory

presentation overview
Presentation Overview
  • Background and device models
  • Filter design
  • L-Bar measurements
  • Parasitic investigations
  • Conclusion
device overview and goals
Device Overview and Goals

18 x 5.5 mm bar with 3.5 mm tethers

  • Desired: a high performance RF channel-select filter bank on a chip
    • 0.3-3 GHz frequencies
    • high selectivity  high Q
    • compatible with silicon IC technologies
    • small size  high density
    • low loss
    • device characteristics defined by lateral geometry

10 x 5 mm bar with 1 mm tethers

device structure
Device Structure

Circuit Model

resonator

Ctethers

longitudinal resonance
Longitudinal Resonance

Longitudinal Mode Shape

  • tethers placed at displacement node
  • longitudinal displacement amplitude on the order of nm
  • other types of mechanical resonances cancel out in charge at lower frequencies
butterworth van dyke model
Butterworth Van-Dyke Model

MTO

MEMS

DARPA

DARPA

C

L

R

C

0

e

r

wl

2

t

l

r

c

8

we

l

p

t

=

=

=

z

=

C

L

C

R

0

2

2

t

tc

p

Q

8

we

8

we

2

bvd impedance function
BVD Impedance Function

8

10

6

10

Impedance Magnitude (W)

4

10

2

10

860

865

870

875

880

885

890

895

900

905

910

90

45

Impedance Phase (degrees)

0

-45

-90

860

865

870

875

880

885

890

895

900

905

910

l = 5.5 mm

w = 3.0 mm

t = 0.5 mm

Q = 10,000

L = 342 mH

C = 0.096 fF

R = 189 W

C0 = 2.98 fF

filter design
Filter Design

Primary Objectives:

  • Review existing crystal filter topologies and assess performance metrics.
  • Down-select a filter topology based on specifications set by RF group.
  • Define fabrication requirements and tolerances to achieve desired performance with each topology
dual resonator ladder
Dual Resonator Ladder

Zs

RS

Vout

Vin

Zp

RL

lattice filter
Lattice Filter

Impedance of Za and Zb

Za

R

Za

Zb

wa

wb

Vin

Vout

R

Zb

Full filter response

Zb

Za

simple ladder filter
Simple Ladder Filter

Z=sL+1/sC

Z=sL+1/sC

RS

Vin

RL

Vout

C12

Wideband Response

-20

-40

-60

Magnitude (dB)

-80

-100

-120

-140

102

103

104

105

106

Frequency (MHz)

simple ladder filter1
Simple Ladder Filter

0

-10

-20

Filter Transmission (dB)

-30

797.5

798

798.5

799

799.5

800

800.5

801

801.5

802

802.5

90

no mismatch

data1

0.1 %

0

data2

0.3 %

data3

-90

Phase (degrees)

-180

-270

797.5

798

798.5

799

799.5

800

800.5

801

801.5

802

802.5

Effect of bar length mismatch on filter characteristic

Nominal values:

l = 6.04 mm

w = 3.22 mm

t = 0.5 mm

RS, RL = 1758 W

C12 = 113.2 fF

slide14

Mechanically Coupled Devices

RS

Vout

Vin

RL

C12

RS

Vout

Vin

RL

C12

device measurement
Device Measurement

Primary Objectives:

  • Confirm successful operation of resonators and accuracy of the analytic model (f vs. l, spurious modes)
  • Fit measurements to a discrete circuit model, adjust model if necessary, and extract resonator parameters (ie, determine resonator Q)
  • Use resonator performance results and analysis of parasitics to guide process and design improvements
device measurement1
Device Measurement

3 mm

5 mm

~800 MHz resonator structure

Device (GSG configuration)

L

C

R

Co

RS

RL

first round devices
First Round Devices

Longitudinal axis

contact

contact

AlN

5 mm Bar, Q=104

0

Cthru=2pF

50

L

C

R

S21 (dB)

Cthru=0

100

675

800 MHz

925

Co

25 mm Bar, Q=103

Rs

10

Cthru

RL

Cthru=2pF

S21 (dB)

20

30

140

180

160 MHz

first round l bar resonance
First Round L-Bar Resonance

-15.5

-15.6

-15.7

S21 (dB)

-15.8

-15.9

-16

73

72

Phase (degrees)

71

70

69

150

147

148

149

146

Frequency (MHz)

Cthru ~ 2 pF

measurement results
Measurement Results

800

-15

Fundamental Length Resonances

-6

600

-16

Frequency (MHz)

-7

25 mm bar

-17

400

~ 3.8 GHz - mm

-8

E

S21 (dB)

1

=

×

-18

2

r

200

-9

-19

600

700

800

900

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

0.18

0.2

30 mm bar

1 / mm

-20

Fundamental Width Resonances

-21

120

130

140

150

160

Frequency (MHz)

Frequency (MHz)

second round l bar
Second Round L-Bar

10 mm x 5 mm device showing length and width modes

-40

-50

S21 Magnitude (dB)

-60

-70

-80

110

100

90

Phase (degrees)

80

70

60

100

200

300

400

500

600

700

800

900

1000

Frequency (MHz)

fit to model
Fit to Model

S21 data from 10mm x 5mm device

  • Parasitics modeled as
  • port capacitance and
  • resistance
  • BVD circuit parameters
  • R= 35 kW
  • L= 1 mH
  • C=0.047 fF
  • C0=12.7 fF
  • Q of ~125
metal oxide silicon structures
Metal-Oxide-Silicon Structures

0

-20

-40

S21 Magnitude (dB)

-60

-80

-100

0

100

200

300

400

500

600

700

800

900

1000

200

100

Phase (degrees)

0

-100

-200

0

100

200

300

400

500

600

700

800

900

1000

Frequency (MHz)

glass substrate
Glass Substrate

OP6 on Glass

  • OP6 fit parameters:
  • pure open to ground
  • 1.43fF thru capacitance

-60

S21 Magnitude (dB)

-80

data

simulation

-100

0

500

1000

1500

2000

2500

3000

150

100

Phase (degrees)

50

0

0

500

1000

1500

2000

2500

3000

Frequency (MHz)

glass substrate1
Glass Substrate

OP1 on Glass

  • OP1 fit parameters:
  • pure open to ground
  • 2.6fF thru capacitance

-60

S21 Magnitude (dB)

-80

data

simulation

-100

0

500

1000

1500

2000

2500

3000

150

100

Phase (degrees)

50

0

0

500

1000

1500

2000

2500

3000

Frequency (MHz)

conclusions
Conclusions
  • Filter designs will be implemented on upcoming mask layout. Mechanically coupled device will be used.
  • An accurate model of parasitics is vital for obtaining useful device measurements.
  • Ongoing work to define explanation for the 100 MHz resonance on silicon substrate, and the wideband phase noise
acknowledgements
Acknowledgements

Draper Engineering

Amy Duwel, David Carter, Doug White

Draper Fellows

Paul Calhoun, Luke Hohreiter

Draper Program Manager

James Sitomer

Acknowledgements:

Draper:Connie Cardoso, Mert Prince, Mark April,

Mark Mescher and Mathew Varghese

MIT:Prof. Charles Sodini

DARPA: Contract # DAAH01-01-C-R204

s parameters
S-parameters

-

V

=

i

S

i j

+

V

=

¹

V

0

,

k

j

j

k

z parameters
Z-parameters

V1 = Z11I1 + Z12I2

V2 = Z21I1 + Z22I2

two port p model
Two-port p model

(

)

(

)

+

+

Z

Z

Z

Z

Z

Z

Z

Z

=

=

=

a

b

c

a

c

c

a

b

Z

Z

Z

11

12

22

+

+

+

+

+

+

Z

Z

Z

Z

Z

Z

Z

Z

Z

a

b

c

a

b

c

a

b

c

Z = Z11Z22-Z122

Z

Z

Z

=

=

=

Z

Z

Z

a

b

c

Z

-

Z

Z

Z

-

Z

22

12

12

11

12

transformed z b impedance data
Transformed Zb Impedance Data

Zb Magnitude and Phase

3

10

|Zp|

2

10

Impedance Magnitude (W)

1

10

|Zs|

0

10

fs fp

1.5

2

2.5

3

2

1

Impedance Phase (radians)

0

-1

-2

1.5

2

2.5

3

Frequency (GHz)

1

=

=

w

2

π

f

s

s

LC

C

=

=

+

w

2

π

f

w

1

p

p

s

C

0

R

=

»

Z

R

s

+

1

j

w

RC

s

0

1

-

j

w

RC

1

p

0

=

»

Z

p

2

2

2

2

w

RC

w

RC

p

0

p

0

bvd model fitting
BVD Model Fitting

Zb

Magnitude and Phase

60

50

40

30

Impedance Magnitude (dB)

data

data

20

model

10

0

2

1

0

Impedance Phase (radians)

-

1

-

2

1.5

2

2.5

3

Frequency (GHz)

R = 2.76 W, L = 91.6 nH, C = 0.061 pF, C0 = 1.54 pF

filter design constraints
Filter Design Constraints

Constraints placed on equivalent circuit parameters by

bar geometry:

  • Q assumed to be a function of the process and static
  • Two degrees of freedom, l and w/t
  • Resonant frequency fixes l uniquely
  • For a given frequency, the other degree of freedom controls the “impedance level”
  • C/C0 fixed by piezoelectric materials parameters
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